Interleukin-23 (IL-23) is the name given to a factor that is composed of the p40 subunit of IL-12 (IL-12beta, IL-12-p40) and another protein of 19 kDa, designated p19. The p19 subunit is structurally related to IL-6, G-CSF, and the p35 subunit of IL-12. The p19 subunit by itself is biologically inactive while the complex of p19 with p40 is active. The active complex is secreted by antigen presenting cells after cell activation. Mouse memory T-cells (CD4 (+)CD45 Rb(low)) proliferate in response to IL-23 but not in response to IL-12. Human monocyte-derived macrophages produce IL-23 in response to virus infection (Sendai virus, but not Influenza A virus).
The IL-23 receptor complex consists of a receptor chain, termed IL23R, and the beta-1 subunit of the IL-12 receptor. IL-23 does not bind to the beta-2 subunit of the IL-12 receptor. The human IL-23R gene is on human chromosome 1 within 150 kb of the gene encoding IL-12Rbeta2. IL-23 activates the same signaling molecules as IL-12: JAK2, Tyk2, and STAT-1, STAT-3, STAT4, and STAT-5. STAT4 activation is substantially weaker and different DNA-binding STAT complexes form in response to IL-23 as compared to IL-12. IL-23R associates constitutively with JAK2 and in a ligand-dependent manner with STAT-3.
Expression of p19 in transgenic mice leads to runting, systemic inflammation, infertility, and death before 3 months of age. The animals show high serum concentrations of the pro-inflammatory cytokines TNF-alpha and IL-1. The number of circulating neutrophils is increased. Acute phase proteins are expressed constitutively. Animals expressing p19 specifically in the liver do not show these abnormalities. Expression of p19 is most likely due to hematopoietic cells as bone marrow transplantation of cells expressing p19 causes the same phenotype as that observed in the transgenic animals.
Biologically active IL-12 exists as a heterodimer comprised of 2 covalently linked subunits of 35 (p35) and 40 (p40) kD. IL-12 acts by binding to both the IL-12beta 1 and beta 2 receptor proteins and thereby induces signaling in a cell presenting both of these receptors. Several lines of evidence have demonstrated that IL-12 can induce robust Th1 immune responses that are characterized by production of IFNγ and IL-2 from CD4+ T cells. Inappropriate Th1 responses, and thus IL-12 expression, are believed to correlate with many autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, insulin-dependent diabetes mellitus, and uveitis. In animal models, IL-12 neutralization was shown to ameliorate autoimmune disease. However, these studies neutralized both IL-12 and IL-23 through the shared p40 subunit.
IL-12 is thought to be important in the development of Th1, or “type 1,” CD4+ T cell responses, whereas IL-23 is thought to be important for the activation of memory CD4+ T cells. Several studies suggest that IL-12 is responsible for generating effective immune responses to intracellular pathogens and tumor cells, while the function of IL-23 in these types of immune responses has yet to be fully described. Therefore, while inhibition of both IL-12 and IL-23 should provide significant therapy for immune-mediated disease, inhibition of IL-12 pathways could limit immunity to pathogens or tumor cells and result in an unwanted risk profile. In contrast, inhibition of only IL-23 could provide therapeutic benefit while leaving IL-12 pathways intact. Thus, effective therapy would be achieved concomitant with a lowered risk profile.
Non-human, chimeric, polyclonal (e.g., anti-sera) and/or monoclonal antibodies (Mabs) and fragments (e.g., proteolytic digestion products thereof) are potential therapeutic agents that are being developed in some cases to attempt to treat certain diseases. However, such antibodies that comprise non-human portions elicit an immune response when administered to humans. Such an immune response can result in an immune complex-mediated clearance of the antibodies from the circulation, and make repeated administration unsuitable for therapy, thereby reducing the therapeutic benefit to the patient and limiting the readministration of the Ig derived protein. For example, repeated administration of antibodies comprising non-human portions can lead to serum sickness and/or anaphalaxis. In order to avoid these and other such problems, a number of approaches have been taken to reduce the immunogenicity of such antibodies and portions thereof, including chimerization and “humanization,” as well known in the art. These approaches have produced antibodies having reduced immunogenicity, but with other less desirable properties.
Accordingly, there is a need to provide anti-IL-23 antibodies or specified portions or variants, nucleic acids, host cells, compositions, and methods of making and using thereof, that overcome one more of these problems.